This Phase 3 European Registration study has been designed to evaluate the efficacy, safety and tolerability of Arikayce™ in treating CF patients with chronic bronchopulmonary infection compared to a currently available antibiotic, TOBI® (tobramycin) Inhalation Solution. Eligible subjects will be randomized 1:1 to receive 590 mg of Arikayce™ once daily via a PARI Investigational eFlow® Nebulizer or 300 mg TOBI® BID via a PARI LC® PLUS nebulizer. Subjects will receive 3 cycles of treatment with each cycle being comprised of 28 days on treatment followed by 28 days off-treatment. Total study duration is up to 186 days (~6 months) including an up to 18 day Screening period. Subjects will be evaluated for safety, tolerability and efficacy bi-weekly during the first 4 weeks of treatment, and thereafter every 4 weeks for the duration of the study. Pharmacokinetics (PK) of Arikayce™ in blood, sputum and 24-hour urine will be determined in a subgroup of study subjects who consent to PK evaluation.